Vacuum mixing/bone cement cartridge and kit

ABSTRACT

A two-component bone cement mixing system comprises a cartridge mixer having an interior volume containing a first predetermined quantity of a solid bone cement component under vacuum pressure; an ampoule containing a second predetermined quantity of a liquid bone cement component; a fluid transfer element for fluidically connecting the cartridge mixer and the ampoule for transfer of the liquid bone cement component to the cartridge mixer; and a plug element, receivable within the ampoule, for automatically hermetically sealing the fluid transfer element against passage of a material therethrough upon completion of the transfer of the second predetermined quantity of the liquid bone cement component into the cartridge mixer. The two-component bone cement mixing system allows in vacuo mixing of liquid monomeric and solid polymeric bone cement components without air being incorporated into the mixture and insures the prevention of air passage into the cartridge mixer during and/or after monomer transfer.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to the mixing of materials in thesubstantial absence of air. More particularly, the present inventionrelates to the preparation of a bone cement from a solid component and aliquid component by admixing the two components under vacuum pressure,an apparatus to effect such mixing and a kit to provide a surgeon withall the necessary materials to prepare a two-component bone cementsubstantially free of entrained air.

Additionally, the present invention relates to a method of preparing abone cement from a solid component and a liquid component by admixingthe two components under vacuum pressure, wherein such admixture takesplace under a predetermined degree of chilling so as to control the rateof hardening of the cement, and subsequently pressurizing the admixtureto inhibit entrainment of gaseous materials.

2. Description of the Prior Art:

In many orthopedic surgical procedures, it is necessary to employ abonding material to set implants such as pins and artificial joints inbone. The cement which is employed for this purpose is generally apolymeric material which is prepared by copolymerization of itscomponents as needed. Because of the necessity for a fairly quicksetting material the cement is almost universally prepared by a surgicalassistant during the course of the operation in the sterile field of theoperating room. The preparation of the cement involves admixture of thecement components in a suitable reaction vessel to form a uniformpolymeric reaction product. The cement is usually a (meth)acrylicmaterial comprising a reaction product of a monomer and a polymer, e.g.methylmethacrylate monomer and polymethylmethacrylate ormethylmethacrylate-styrene copolymer. In order to provide a cement whichhas the desired properties and which has the desired fixation of theimplants, it is necessary that the compounds be uniformly and thoroughlymixed so that a homogeneous reaction product is produced. During themixing and subsequent reaction, there are produced various vapors whichmay comprise a gaseous form of a volatile component or a gaseousreaction product. Because of the noxious (and toxic) nature of suchvapors it is highly undesirable to be exposed to them, particularly forextended periods of time in the course of multiple preparations. Sinceit is necessary that the mixing be carried out for extended periods oftime in order to ensure a uniform reaction product and a minimumconcentration of volatile reactants, the period of exposure to harmfulvapors can be substantial.

Nonetheless, despite the knowledge of the aforesaid difficulties, allknown techniques for the mixing of bone cements have serious drawbacks,the most frequent being:

poor mixing, depending on the individual mixing technique;

high exotherm, due to considerable amounts of monomeric componentnecessary to produce a workable cement mass by conventional mixingtechniques; and

creation of porosities, by inclusion and entrapment of air bubbles aswell as by evaporation of excess monomer resulting in the degradation ofthe mechanical properties of the cured cement.

In order to avoid these problems, various attempts to provide vacuummixing devices have been made.

U.S. Pat. No. 4,185,072, to Puderbaugh et al., discloses an orthopediccement mixer which comprises a mixing vessel within an evacuable housingand mixing vanes operable from outside of the housing. The housing isprovided with vacuum conduits which can be connected to a vacuum sourcefor withdrawing vapors and/or gaseous reaction products from within thehousing.

U.S. Pat. No. 4,277,184, to Solomon, discloses a disposable orthopedicimplement for mixing and dispensing bone cement comprising a chamberhaving a barrel portion and a neck portion; a member which isreciprocable within the barrel portion of the chamber; a mixing memberoperatively and axially receivable within the reciprocable member; andmeans for rotating the mixing member within the barrel portion of thechamber.

U.S. Pat. No. 4,463,875, to Tepic, discloses an apparatus for preparingand applying a two-component cement, wherein the components are vacuumpackaged in elongated flexible fluid-tight compartments and thosecompartments are confined in abutting relation with a seal existingaround the abutting portions of the compartments. In operation, one ofthe compartments is gradually collapsed to force its contents to breakthrough the abutting wall portions into the other compartment while theextension of the other compartment is controlled as it receives thecontents of the one compartment. Then the other compartment is graduallycollapsed to force its contents into the one compartment whilecontrolling the extension of the one compartment. The two compartmentsare alternately collapsed and controlledly extended until the componentstherein form a homogeneous cementitious mixture. A nozzle is thenattached to one of the compartments in lieu of the other compartment andthe one compartment is collapsed to expel the mixture through thenozzle.

Published International patent application WO 84/03830, to Himeno,discloses an apparatus for mixing a bone cement wherein the solidcomponent of a bone cement is sealed in a flexible bag along with asterilizing gas. The gas is then withdrawn through a hypodermic needleto evacuate the gases within the bag. The liquid component of the bonecement is then injected into the bag, and the bag kneaded to mix thecement. After kneading the bag may be opened to remove the ready-to-usecement.

U.S. Pat. No. 4,551,135, to Gorman et al., discloses a syringe forextrusion of a semi-plastic mass. The syringe is designed so as topermit the mixing of two components of a plasticizable mixture withinthe syringe barrel, i.e. a liquid component may be injected into thesyringe barrel containing particulate solids while venting air therefromor a liquid component may be drawn into the syringe barrel which is onlypartially filled with particulate solids.

European Published patent application No. 0 178 658 (and U.S. Pat. No.4,721,390), to Lidgren, disclose a method for producing bone cement forfixing prostheses. In order to prevent large amounts of air from beingstirred into the mixture, mixing of the bone cement components occursunder vacuum. Preferably the bone cement components are mixed in a feeddevice from which the mixture may be pressed out, and to effect thisaspect of the invention there are provided an agitator which isconnectable to the feed device and a vacuum source which is alsoconnectable to the feed device.

Published International patent application WO 86/06618, to Tepic,discloses a method of preparing a two component cement wherein theevacuated interspaces between powder component particles are floodedwith liquid component, followed by mechanical homogenization of theresulting mass. The method is preferably performed in a syringe-typecontainer whereby the liquid component in an ampoule is injected throughthe piston member of the syringe, and the syringe is fitted with anaxially collapsible mixing element, so as to not interfere with movementof the piston for extrusion of the cement from the syringe.

U.S. Pat. No. 4,671,263, to Draenert, discloses a device for applyingbone cement wherein the bone cement, prior to its application, isprepressurized at an adjustable pressure and then applied at acontrollable pressure. The prepressurization suppresses bubble formationin the bone cement and the controllable pressure aids desiredstratification of the bone cement around the prosthesis duringapplication.

The brochures "MIT VAC® Vacuum Mixing System" and "ZIMMER® Vacuum MixingSystem" (Copyright 1986) both disclose a bone cement mixing systemproviding a vacuum pump and either an evacuable mixing bowl; or anevacuable housing (with mixer), for mixing in a cartridge for a bonecement gun.

The brochure "DePuy Vacu-Mix® Orthopedic Cement Mixing System"(April1977) discloses an open housing, for a mixing bowl, which may beconnected to a vacuum pump so as to draw off vapors from above themixing bowl.

The brochure "Stryker® Mix Evac®" (copyright August 1978) discloses adisposable enclosed housing which comprises a mixing vessel within ahousing, a cover for the housing and a mixing element operable throughthe cover. The housing may be connected to a vacuum supply to draw airthrough the cover and out through the housing thus preventing monomervapors from being released to the operating room atmosphere.

The advertisement "The Simplex Enhancement Vacuum Mixer", JBJS, No. 2,69-A, February 1987, discloses an evacuable housing, having a coverequipped with an externally operable mixing element, which will hold abone cement gun cartridge for mixing of bone cement in the cartridge.The housing may be connected to a vacuum source to allow mixing undervacuum pressure.

The brochure "ZIMMER® Cement Centrifugation System"(Copyright 1984)discloses a system wherein after mixing of the bone cement, the bonecement is placed in a cartridge for a bone cement gun and centrifuged tohelp decrease cement porosity.

Numerous other devices have been conceived for the conduct of mixingoperations under a controlled atmosphere or under vacuum. Illustrativeof such devices are U.S. Pat. No. 2,453,914, to Hollenback, whichdiscloses a device for mixing plaster compounds comprising a bowl, acover for said bowl which carries an externally operated mixer for theagitation of the bowl contents and an orifice for attachment to a vacuumsource to de-aerate the bowl contents.

U.S. Pat. No. 2,696,022, to Steinbock et al., discloses an investmentmixer comprising a mixer bowl, a cover therefor, an agitator extendingthrough the cover, and a fitting on the cover for connection to a vacuumsource.

U.S. Pat. No. 2,973,187, to Wehmer, discloses a vacuum spatulatorcomprising a mixer bowl, a cover therefor, an agitator extending throughthe cover, and a fitting whereby the covered bowl may be placed undervacuum.

U.S. Pat. No. 3,131,912, to Steinbock, Jr., discloses an investmentmixer comprising a mixing bowl, a cover for the mixing bowl, anexternally operated agitator extending through the mixing bowl, and afitting on the cover allowing evacuation of the atmosphere in the mixingbowl by connection to a vacuum source.

U.S. Pat. No. 3,343,817, to Carangelo et al., discloses an apparatus formixing materials in the absence of air comprising a mixing bowl havingan externally operated agitator in the bottom thereof and a pistonreceivable within the mixing bowl. The piston has an aperture therein sothat, when it is lowered into place on materials to be mixed in thebowl, air caught below the piston is expelled. When the piston contactsthe surface of materials to be mixed, the aperture is closed andagitation initiated.

U.S. Pat. No. 3,358,971, to Steinbock, Jr., discloses an investmentmixer comprising a mixer bowl, a cover therefor, an agitator extendingthrough said cover into said mixing bowl and an aperture for removinggases within the mixing bowl by connection to a vacuum pressure supply.

U.S. Pat. No. 3,559,961, to Bergendal, discloses an apparatus for thepreparation of dental amalgams comprising a container of two halves, oneof which is fitted with an outlet connectable to a vacuum pressuresupply. Components to be formed into an amalgam are placed within thecontainer, the container atmosphere is evacuated, and the evacuatedcontainer is then agitated to mix the contents thereof.

U.S. Pat. No. 3,610,586, to Price et al., discloses a dental mixingsystem in which prepackaged ingredients to be mixed for dentalapplications are stored within a container which maintains theingredients isolated from each other prior to usage. The ingredients areintermixed by placing the container in a mixing device which rotates thebase of the container while maintaining the cover stationary. A knifeportion integral with the container bottom severs an isolating membranestretched over a portion of the cover, during operation of the mixer,and permits the ingredients to mix. Through rotation of the containerbottom, a homogeneous mixture is realized with a mixing paddle integralwith the stationary container top or cover.

U.S. Pat. No. 3,640,510, to Lea, discloses a vacuum mixing system fordental materials comprising a closed container, an externally operatedrotary stirring device therein and means for applying vacuum pressure tothe contents of the closed container.

U.S. Pat. No. 4,199,866, to Drury, discloses a dental amalgamator whichprevents mercury vapor, given off during amalgamation, from pollutingthe air in the neighborhood of the amalgamator. The amalgamatorcomprises a casing carrying a capsule holder and a drive means for theholder, a lid movable to a closed position in which it cooperates withthe casing to form an enclosure for a capsule held by the holder, theenclosure having air inlets allowing air to flow from the atmosphereinto the enclosure. A vacuum pump is arranged to communicate with theenclosure via a mercury filter medium, so that during amalgamation airis drawn into the enclosure, over the capsule, and then through themercury filter where mercury vapors are removed.

Nonetheless, a need continues to exist for a simple two-component bonecement mixing system, which will allow mixing under vacuum but whichwill require little in the way of equipment. Moreover, a need alsoexists for a vacuum mixing system which can be readily manipulatedwithout fear of premature loss of vacuum.

SUMMARY OF THE INVENTION

In a first embodiment, the present invention provides a two-componentbone cement mixing system comprising:

(A) a cartridge mixer means, having an interior volume containing afirst predetermined quantity of a solid bone cement component undervacuum pressure, for mixing said first predetermined quantity of a solidbone cement component with a second predetermined quantity of a liquidbone cement component in the substantial absence of air to form a thirdpredetermined quantity of a fluid two-component bone cement;

(B) container means, containing said second predetermined quantity of aliquid bone cement component, for holding a liquid bone cementcomponent;

(C) fluid transfer means, operably connectable to said cartridge mixermeans and said container means, for fluidically connecting saidcontainer means and said cartridge mixer means to transfer said secondpredetermined quantity of a liquid bone cement component from saidcontainer means to said cartridge mixer means;

(D) plug means, receivable within said container means, forautomatically hermetically sealing said fluid transfer means againstpassage of a material therethrough upon completion of the transfer ofsaid second predetermined quantity of a liquid bone cement componentfrom said container means to said cartridge mixer means therethrough.

In a second embodiment, the present invention provides a cartridgemixer, having an interior volume, useful for the mixing of a firstpredetermined quantity of a solid bone cement component with a secondpredetermined quantity of a liquid bone cement component to form a thirdpredetermined quantity of a fluid two-component bone cement, saidcartridge mixer comprising

cartridge means, receivable within a bone cement gun, for containingsaid third predetermined quantity of a fluid two-component bone cement,said cartridge means including piston means, operatively engageable bysaid bone cement gun and moveable within said cartridge means, fordispensing of said fluid two-component bone cement from said cartridgemeans;

mixer means, detachably connected to said cartridge means, for agitatingthe contents of said cartridge means, said mixer means including inletport means for passage of a second predetermined quantity of a liquidbone cement component into said cartridge mixer;

hermetic sealing means for sealing said connected cartridge means andmixer means against the ingress of air.

In a third embodiment, the present invention provides a two-componentbone cement kit comprising:

(A) a vacuum packed cartridge mixer, defining an interior volume,containing a first predetermined quantity of a powdery bone cementcomponent, said cartridge mixer comprising:

a cartridge member, receivable within a bone cement gun, comprising ahollow, air-impermeable cartridge body member having a longitudinalaxis, and a first open end and a second open end spaced apart on saidlongitudinal axis,

an air-permeable piston member, axially slidable within said hollowcartridge body, disposed within said cartridge body, proximate saidfirst end of said cartridge body, to close said first end of saidcartridge body,

releasable hermetic sealing means for releasably hermetically sealingsaid piston member to said cartridge body proximate said first end ofsaid cartridge body,

a mixer member comprising a hollow, air-impermeable mixer body having alongitudinal axis, and a first open end and a second open end spacedapart on said longitudinal axis,

releasable connection means for releasably coaxially hermeticallysealingly connecting said second end of said cartridge body member tosaid second end of said mixer body for fluidic communication betweensaid cartridge body member and said mixer body, and

cap means for hermetically sealing said first end of said mixer body,said cap means including

self-sealing aperture means, pierceable by a hollow needle, for fluidiccommunication with said interior volume of said cartridge mixer throughsaid hollow needle when pierced by said hollow needle and hermeticallysealed closure of said interior volume when said hollow needle iswithdrawn, and

mixing means for agitating a material contained within said interiorvolume of said cartridge mixer;

(B) an ampoule, defining an interior volume, containing a secondpredetermined quantity of a liquid bone cement component, said ampoulecomprising a liquid bone cement component impermeable body member havinga longitudinal axis, spout means, having a predetermined diameter, forfluidic communication with said interior volume of said ampoule andremovable closure means for hermetically sealing said spout means;

(C) an injector comprising

a hollow injector body member having a longitudinal axis and a firstopen end and a second open end spaced apart on said longitudinal axis,said hollow injector body member slidingly, coaxially receivable of saidampoule,

a cap member, disposed on said second open end of said hollow injectorbody for closure thereof, said cap member including a fluid conduit,coaxial with said hollow injector body, for passage of a fluid throughsaid cap member,

hollow needle means, pierceable of said self-sealing aperture means,hermetically connectable to said fluid conduit, for passage of fluidinto said interior volume of said cartridge mixer,

resilient support means, hermetically sealingly connecting said secondend of said hollow injector body and said cap member, for engaginglycontacting said ampoule, said resilient support means including a fluidpassage tapering toward and fluidically connected to said fluid conduit,said fluid passage coaxial with said hollow injector body and receivableof said ampoule spout means; and

(D) float means, having a specific gravity less than said liquid bonecement component, for hermetically sealingly closing said fluid passagein said resilient support means.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a schematic, partially sectioned, illustration of a doublevacuum-packed cartridge mixer according to the present invention.

FIG. 2 is an isometric view of a bone cement cartridge according to thepresent invention.

FIG. 3 is a schematic, partially sectioned, illustration of a firstembodiment of a releasable hermetic closure for a piston of a bonecement cartridge.

FIG. 4 is a schematic, partially sectioned, illustration of a secondembodiment of a releasable hermetic closure of a piston of a bone cementcartridge.

FIGS. 5A and 5B are schematic, partially sectioned, illustrations of athird embodiment of a releasable hermetic closure of a piston of a bonecement cartridge.

FIG. 6 is an illustration of a container for liquid bone cementcomponent.

FIG. 7 is a schematic, partially sectioned, illustration of a liquidbone cement injector according to the presently claimed invention.

FIG. 8 is a sectional view of a bone cement gun containing a bone cementcartridge.

FIGS. 9A and 9B are schematic, partially sectioned illustrations of apressure gauge for prepressurization of a bone cement cartridge.

FIG. 10 is a sectional view of the application of bone cement to a bonecavity in a bone.

FIG. 11 is a view partially in section illustrating the deposition ofbone cement into the femoral canal.

FIG. 12 is a sectional view illustrating pressurization of bone cementin the federal canal.

FIG. 13 is a detailed view of the capped end of the mixer body.

FIG. 14 is a plan view of the underside of the cap fixed on the firstopen end of the mixer body.

FIG. 15 is a plan view of a protective disc mounted on the underside ofthe cap fixed to the first open end of the mixer body.

FIG. 16 is a plan view of the mixing element according to the presentinvention.

FIG. 17 is an illustration of a technique for testing for operability ofthe bone cement prepared according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It is common practice, in joint surgery today, to anchor components ofreplacement joints by using a bone cement comprising a two-componentresin which polymerizes during the operation at normal temperatures andwhich, on account of its properties, leads to an interlocking of theprosthesis component in the bony sheath. Because of its physicalproperties, the bone cement shrinks onto the prosthesis resulting in aclosed metal-to-cement contact.

The bone cements commonly used are polymethylmethacrylate consisting ofpowdery bead polymers which are superficially dissolved by liquidmonomers and embedded during the polymerization process. During mixing,the polymer is immersed in the monomers. The polymethylmethacrylatebeads are superficially dissolved and embedded in a composite manner.Such a composite structure can be compared with concrete, where airbubbles are likewise included during mixing. Moreover, when the monomerimmerses the polymer beads, filling defects remain. These defects aretermed "lee phenomena". Furthermore, in the case of bone cements, themonomer liquid evaporates during the exothermic polymerization, wherebyfurther bubbles are formed. The bubbles formed as mentioned aboveconstitute the major portion of the gas enclosures in bone cements.

The chemical reaction of the above-mentioned bone cements is initiatedby a starter reaction, wherein, typically, dibenzoyl peroxide isactivated by an activator such as p-aminotoluidine and then the radicalchain polymerization is started. This polymerization proceedsexothermically. The monomer itself is stabilized by hydroquinone. Somebone cements are further stabilized by chlorophyll with simultaneouscoloring. The storability of the monomer liquid can also be stabilizedby vitamin C.

In the processing phase, following the mixing phase, the bone cement isapplied to the femoral medullary canal or to the bony acetabulum whichare both prepared to anchor the cemented prosthesis components; theapplication of the bone cement is normally performed by hand andsometimes using a syringe.

Using a syringe, the cement anchorage in the bone can be markedlyimproved. Therefore, so-called "bone cement guns" have been proposed,the principal of which is to impact the cement in the plugged medullarycanal to provide transverse anchorage. With bone cement guns, thefilling of the bone bedding is performed in different ways. On the onehand, filling is done from above in the downward direction or, on theother hand, it is also performed in the other direction, i.e. upwardlyfrom below, by means of a long nozzle.

With the aforementioned techniques in mind, the present inventionprovides a two-component bone cement mixing system which allowspreparation of the two-component bone cement under vacuum pressure,whereby gaseous inclusions are minimized, and further allows thepreparation of the bone cement in a cartridge which may then be directlyloaded into a bone cement gun for immediate operative use.

Turning now to FIG. 1 of the drawing, there is generally indicated at 1a double vacuum-packed cartridge mixer according to the presentinvention. The cartridge mixer comprises a cartridge member 3 and amixer member 5 which are detachably connected to each other. Thecartridge member 3, as best seen in FIG. 2, comprises a hollow,air-impermeable cartridge body member 9 having a flange 11 at one endthereof along with a collar 13 whereby the cartridge body member may bemounted in a bone cement gun, as best seen in FIG. 8. The wall of thecartridge body member 9 may be reinforced with ribs 15 for addedstrength.

An air-impermeable piston member 17 is disposed within the cartridgebody 9 proximate a first end 19 thereof so as to close the first end ofthe cartridge body member 9. The piston member 17 is axially slidablewithin the hollow cartridge body 9.

The mixer member 5 comprises a hollow, air-impermeable mixer body 21having a first open end 23 and a second open end 25. The second open end25 of the mixer body member 21 is provided with an internal screwthread(not shown) which is threadingly engageable of a screwthread 27 formedon the exterior of the second open end 7 of cartridge body member 9. Byproviding an O-ring 29 abutting the reinforcing rib 15' a releasablecoaxial hermetic seal of the cartridge body member to the mixer bodymember may be obtained when the cartridge body member and the mixer bodymember are threadingly engaged with one another. Of course, any otherform of detachable connection capable of forming a hermetic seal mayalso be utilized, e.g., a snap-fit with O-ring sealing element. In asimilar manner, the cap 31 in combination with an O-ring 33 hermeticallyseals the first end 23 of the mixer body member 21. The cap 31 includesan aperture 35 which is closed by a self-sealing element 37 such as arubber septum. The cap 31 is also provided with an additional aperture39 through which the shaft 41 of a mixing element 43 passes. The shaft41 is axially moveable in the aperture 39 and may also be rotated withinthe aperture 39. As may best be seen in FIG. 13, the aperture 39 issurrounded by an upstanding, circumferential wall 32 which forms achamber 34 receivable of a plurality of alternating O-rings and washers(two O-rings 36 and 38 and one washer 40 being illustrated). The chamber34 is closed by a cap member 42 which is threadingly engageable with theouter circumference of wall 32, the cap member 42 having an aperture 44therein to allow passage of shaft 41 therethrough. The use of multiple0-rings alternating with washers (to form a packing box) is necessary inorder to allow for reciprocal movement of shaft 41 while maintainingvacuum pressure within the mixer. The underside of the cap 31 (as bestseen in FIG. 14) has a number of interconnected grooves 48 formedtherein, with at least one of the grooves communicating with aperture35. A porous membrane 47, e.g., a filter paper, is disposed over theunderside of cap 31 so as to cover the grooves 48. The porous membrane47 has an aperture 50 formed therein so as to permit passage of shaft 41therethrough. The porous membrane 47 is in turn covered by a protectivedisc 52 (as best seen in FIG. 15). The protective disc 52 has a centralaperture 54 to permit passage of shaft 41 therethrough. The protectivedisc 52 is additionally provided with a plurality of apertures 56 (whichmay vary in size, shape and pattern). The protective disc 52 protectsthe porous membrane 47 from being torn by mixing element 43. Thefunction of the grooves 48, the porous membrane 47 and the protectivedisc 52 will be explained hereinbelow. As best seen in FIG. 16, themixing element 43 comprises a plate 60 disposed substantiallyperpendicular to the shaft 41 and conforming substantially to theinternal cross section of the cartridge body member and the mixer bodymember. The mixing element 43 has a number of holes 62, 64 formedtherein so as to allow the mixer element to be reciprocated back andforth through a body of polymeric material 46 contained within thecartridge body member 9. The shaft 41 is provided with a manuallygraspable handle 45 so as to facilitate manipulation of the mixingelement 43. In a preferred embodiment, the holes 62, 64 are circular inshape and disposed symmetrically about the plate 60 relative to theshaft 41 (which is concentric with the plate 60). The plate 60 is alsocircular in shape, and pairs of holes (one larger 64 and one smaller 62)are disposed on diameters of the plate and opposite one another relativeto the center of the plate. Most preferably, three pairs of holes areused disposed on diameters of the plate which are offset 60° of arc fromthe adjacent diameters upon which holes are disposed; and each largehole 64 is immediately adjacent to two small holes 62 on the immediatelyadjacent diameters upon which holes are disposed. The centers of thesmaller holes 62 all fall on the circumference of a first circleconcentric with the plate 60; and the centers of the large holes 64 allfall on the circumference of a second circle concentric with the plate60. Preferably, the diameter of the first circle is larger than thediameter of the second circle.

In use, the cartridge member 3 is loaded with a predetermined amount ofa powdery polymeric component 46 and the mixer member 5 is then screwedonto the cartridge member so as to form a closed container. A hypodermicneedle connected to a source of vacuum pressure is then inserted throughthe rubber septum 37 in aperture 35 and a vacuum is drawn within thecartridge mixer. Care must be taken so that the tip of the needle mayenter the groove 48 but does pierce the porous membrane 47. This isbecause the powdery polymeric material would otherwise be sucked upthrough the needle and block further evacuation of air. The grooves 48,accordingly, allow a uniform application of vacuum across thecross-section of the mixer, while the porous membrane 47 preventspowdery polymeric material from being withdrawn from the mixer alongwith the air. The protective disc 52, in turn, prevents the mixerelement 43 from damaging the porous membrane during handling prior toevacuation. Typically, a vacuum pressure of 30 millimeters of mercury orless is drawn in the cartridge mixer. The vacuum packed cartridge mixeris then vacuum packed within a container 49, such as an air-impermeableplastic bag. This double vacuum packing helps to assure a long andstable shelf life.

In order to provide a hermetic seal of the cartridge mixer, it isnecessary that the piston member 17 be hermetically sealed also.However, the piston member 17 must also be axially slidable within thecartridge body member 9 so as to be capable of forcing the fluid bonecement from the cartridge member when the cartridge member is mounted ina bone cement gun. In other words, the piston member is not fittedwithin the cartridge member in an air tight manner, but rather justsufficiently tight to prevent leakage of the viscous cement mixturethereby. Accordingly, a releasable hermetic seal is necessary for thepiston member. In this regard, FIG. 3 illustrates one embodiment of areleasable hermetic seal for the piston member 17 wherein a bead 51 ofadhesive seals the piston in place. When the piston is engaged by theplunger of a bone cement gun, the bone cement gun plunger developssufficient force to break the bead and allow movement of the pistonthrough the cartridge body member 9. In a second embodiment, illustratedin FIG. 4, a thin layer of a resinous material 53 (e.g., polyethylene)is disposed over the piston member 17. In a manner similar to that ofembodiment FIG. 3, the thin layer resinous material 53 may be broken byactuation of the plunger of a bone cement gun.

In a further embodiment, illustrated in FIGS. 5A and 5B, a thindiaphragm layer 55, e.g. of polyethylene, which is air-impermeable, isdisposed across the first end 19 of cartridge body member 9 as shown inFIG. 5A to form the hermetic seal. When a vacuum is drawn in theinterior of the cartridge mixer, the diaphragm layer 55 is bowed at 57as shown in FIG. 5B. This embodiment not only provides a releasablehermetic seal, which may once again be broken by the actuation of theplunger of a bone cement gun, but also provides an indicator as to themaintenance of vacuum pressure within the cartridge mixer. In thisregard, if the diaphragm layer 55 is bowed as shown in FIG. 5B, thenthis is a clear indication that vacuum pressure has been maintainedwithin the cartridge mixer. If, however, after standing for long periodsof time, a user finds the diaphragm layer 55 in the position illustratedin FIG. 5A, then this is a clear warning that vacuum pressure has beenlost.

The liquid bone cement component 59 is preferably contained within aglass ampoule 61 due to the noxious and toxic nature of the liquid bonecement component, i.e. a (meth)acrylate monomer. The glass ampoule 61comprises a body member 63 having a spout 65 and a removable closure 67which may be broken off at the weakened neck 69 of the ampoule whendesired.

An injector 71, as illustrated in FIG. 7, is utilized to transfermonomer to the interior of the cartridge mixer. The injector comprises ahollow injector body member 73 having a first open end 75 and a secondopen end 77. The injector body member 73 is coaxially receivable of theampoule 61.

A cap 79 is disposed over the second open end 77 of the injector body 73for closure thereof. The cap member 79 includes a fluid conduit 81,coaxial with the hollow injector body member 73, for passage of a fluidthrough the cap member. A hollow needle 83 is hermetically connectableto the fluid conduit 81 so as to allow a fluid medium to pass from theconduit 81 through the hollow needle. A resilient support 85, e.g., ofsilicone rubber, hermetically, sealingly connects the second end of thehollow injector body and the cap member. Additionally, the resilientsupport is provided with a fluid passage tapering toward and fluidicallyconnected to the fluid conduit 81 in the cap member 79. When the openedampoule 61 is inserted into the hollow injector body member 73, and theassembly then inverted to the position of FIG. 7 the resilient support85 supports the ampoule and the spout portion 65 of the ampoule isreceived within the fluid passage 87.

It should be noted that temperature control is an important part of themixing process. For the "dough" type cements in current use, such asSimplex® and Zimmer-Regular®, it has now been found that chilling themixing container and the cement components aids in the prevention ofexcessively fast curing. In particular, when mixing cements under avacuum pressure of 30 mm Hg or less, it has now been found desirable tochill the mixer and the cement components (powder and liquid) to atemperature below room temperature (20° C.), preferably less than 15°C., most preferably to about 12° C. (±2° C.), prior to bringing thesolid and liquid components together in the mixer. This chilling isbelieved to be necessary due to the fact that, under vacuum pressures of30 mm Hg or less, oxygen, which normally interacts with monomer freeradicals to slow the polymerization of the monomer, is in short supplyand will not effectively inhibit the polymerization reaction. In thisregard, a thermometer or a temperature indicating strip, e.g., of theliquid crystal type, could be packaged with the mixer so as to allow theuser to ascertain whether the mixer and its contents have beensufficiently chilled prior to use.

Prior to insertion of the opened ampoule 61 into the injector bodymember 73, a polyethylene ball 89 is placed in the ampoule, thepolyethylene ball having a specific gravity less than the monomericmaterial and thus floating on the surface of the monomeric material.When the injector 71 is inverted so as to insert the needle 83 throughthe rubber septum 37 of the cartridge mixer, so as to inject monomericmaterial into the vacuum packed polymeric material contained therein,the polyethylene ball 89 will float on the surface of the monomer asillustrated in FIG. 7. As the monomer is drained from the ampoule 61through fluid passage 87, fluid conduit 81 and hollow needle 83 into thecartridge mixer, by the vacuum pressure maintained in the cartridgemixer, the polyethylene ball will drop downward with the surface 91 ofthe liquid monomeric material. When the monomeric material is drainedfrom the ampoule the polyethylene ball 89 will then hermetically sealthe fluid passage 87 formed in the resilient support 85. This willprevent any air being drawn into the cartridge mixer around the edge ofthe ampoule 61 and between the ampoule 61 and the hollow body member 73.Thus, personnel transferring monomer to the polymeric material in thecartridge mixer are not required to closely monitor the progress of suchtransfer as they are with conventional syringe techniques orconventional stop cocks. In other words, when the contents of theampoule are emptied, the fluid passage 87 is automatically sealed by thepolyethylene ball 89 acting as a floating plug. Once transfer of themonomer has been completed, the needle 83 may be withdrawn from septum37, and mixing of the two-component bone cement may then be conductedwithin the cartridge mixer. When the hollow needle is withdrawn from thecartridge mixer, air rushing through the hollow needle 83 will violentlydisengage the polyethylene ball 89 from the fluid passageway 87 inresilient support 85. This violent disengagement will cause thepolyethylene ball 89 to bounce around within the empty ampoule 61. Thenoise so-produced is a further indication that a successful transfer ofmonomer into the cartridge mixer has been carried out without leakage ofair into the cartridge mixer.

Mixing is readily effected by merely causing reciprocating motion of themixing element 43 axially within the cartridge mixer. Mixing may befurther facilitated by some rotation of the handle 45 during thereciprocating motion of the mixing element 43.

After mixing is completed, rubber septum 37 may then be pierced with ahollow needle so as to release the vacuum pressure within the cartridgemixer. Alternatively, the mixer member 5 may be provided with a venthole 12 (shown as formed in the mixer body 21, but also could beprovided in the cap 31) hermetically sealed with a pressure-sensitiveadhesive tape 14; and it would only be necessary to peel away the tapeto open vent hole 12 and release the vacuum. The mixer member 5 may thenbe detached from the cartridge member 3 and a suitable cap 93, as bestseen in FIG. 8, may be placed over the second open end 7 of thecartridge body member 9. The cartridge body member 9 may then be fittedin a conventional bone cement gun 95 as illustrated in FIG. 8.

The bone cement may then be utilized in a normal fashion, or, it may besubjected to a prepressurization treatment, which has been found to beeffective in certain instances. In this regard, it should be noted thatin order to minimize the amount of air entrapped in the viscous mixtureas air bubbles, the mixer is maximally evacuated of air. When the liquidmonomer component of the bone cement is introduced into the mixingchamber, a small amount of the monomer will evaporate and equilibrate atthe partial vapor pressure of the liquid monomer at that temperature.However, turbulence created by the mixer element during mixing, i.e.cavitation, will cause the monomer to boil. With higher vacuums, themixture "cavitates" more easily. The monomer which boils under theseconditions, and hence the bubbles of gaseous monomer formed in viscousmixture will only partially collapse when the vacuum is released, andmay require a significant amount of time to collapse fully. Since mostbone cements harden within about 8 to 15 minutes of mixing, the monomerbubbles may not have fully collapsed before hardening. Moreover, theheat of polymerization generated during the curing of the bone cementmay actually cause the partially collapsed gaseous monomer bubbles tore-expand. Therefore, it has been found to be desirable to pressurizethe bone cement shortly after release of the vacuum, but prior to use,hence the name "prepressurization" to accelerate the complete collapseof bubbles of gaseous monomer.

In order to effect the prepressurization treatment, the presentinvention provides a special pressure gauge cap 97 which may be fittedover the second open end 7 of the cartridge body member 9.

As illustrated in FIG. 9A, the cap 97 comprises a flexible membrane 99having two protrusions 101, 103 extending substantially perpendiculartherefrom; and a flange member 105 which may be screwed onto the end ofthe cartridge body member. The flange member incorporates an arcuategauge element 107 having predetermined indicia 109 and 111 formedthereon. When the cartridge body member is mounted in the bone cementgun and subjected to pressure by movement of the plunger of the bonecement gun and concomitant movement of the piston member of thecartridge member, the increase in pressure causes distension of themembrane 99, as best seen in FIG. 9B. The distension of this membranemember causes the protrusions 101 and 103 to effectively bend outwardlyaway from one another and the degree of this bending is indicative ofthe internal pressure developed in the cartridge body member. Byapplying pressure until such time as the indicia 109 and 111 aresubstantially aligned with the protrusions 101 and 103, respectively, apredetermined pressure may be developed within the cartridge bodymember. After maintaining the pressure, e.g. 75 psig, for apredetermined period of time, the pressure may be released and the cap97 removed.

In operation, a closure cap 120 may then be connected onto the open end7 of the cartridge 9, as illustrated in FIG. 10, and a tip 121 isselected for the particular type of operation and is engaged with thefront closure cap 120. (At this point, it is recommended that the firstfew cc's of the cement be wasted by squeezing the handle of the cementgun. This would allow the surgeon a feel of the flow (viscosity) of thecement from the nozzle of the cement gun prior to injecting it into thepatient. If the cement is too stiff, the surgeon should abandon the useof the cement. Alternatively, the temperature of the cement isindicative of the degree of cure and the temperature may be used as thedeterminative factor in whether or not the cement should be utilized. Inthis regard, as shown in FIG. 17, a temperature sensitive tape, e.g., ofthe liquid crystal type, 150 may form the wall of a small container intowhich a few cc's of cement 152 is injected. Depending upon the type ofcement utilized, the tape will have a temperature range in which furtherutilization of the cement is permissible ("OK") and above a certaintemperature further utilization of the cement is not permissible("ABORT"). One indicia, "OK" or "ABORT", only will be readily visibledepending on the temperature of the cement. The engagement between thefront closure cap 120 and the cartridge body member may be by means of asnap fit, an internal threading or an external threading. When aprosthesis is to be cemented to a plateau-type surface, holes 122 may bedrilled into the bone surface to create a cavity into which bone cement123 is to be injected, as shown in FIG. 10. An appropriate tip isselected which is configured to interfit with the opening of the bonecavity. The end of the tip is tapered inwardly to terminate in a portionhaving a diameter less than the diameter of the bone cavity. This allowsthe tapered portion of the tip to be inserted into the bone cavity andform a seal about the diameter of the bone cavity. Thus, the cement isinjected into a closed space so that pressure can build up to force thecement to penetrate the trabeculae of the bone. Cement is also depositedover the remaining bone surface to which the prosthesis is to beattached.

In the case of a long tubular bone canal, some type of plug as shown inFIG. 11 must be lodged in the canal to create a closed space to preventthe extension of bone cement beyond the point where it is useful and tofacilitate more complete filling and pressurization of the canal.Various means of plugging the canal have been advocated, including plugsmade of natural bone, polyethylene or a bolus of doughy bone cement.Initially, a long straight tip 121b, which has a diameter less than thediameter of the canal to allow the tip to project into the bone canal,is used to deposit bone cement into the long bone canal. This tip 121bdoes not have a tapered end since the canal is initially just beingfilled up. Then, a tip such as the femoral canal pressurizer 140 andadapter 141, as shown in FIG. 12, is used to complete the filling of thecanal and pressurize the contents of the cavity. The tapered pressurizerseals off the canal thereby enabling the pressure created upon injectionof the cement to force the cement to penetrate the bone.

Throughout the specification, reference has been made to theair-impermeability of certain materials of construction which areutilized in the present invention. It should be noted that thisterminology does not require perfect air-impermeability, however, itdoes require a degree of air-impermeability sufficient to prevent anysignificant loss of vacuum pressure through the material over theexpected storage life of the vacuum packed materials, e.g. six months.

The mixing system disclosed in the present invention may be provided inthe form of a kit comprising a double vacuum packed cartridge mixerfilled with a first predetermined amount of a solid, powdery bone cementcomponent, an ampoule containing a second predetermined amount of aliquid bone cement component, an injector for transfer of the liquidbone cement component to the cartridge mixer and a polyethylene ball forinsertion in the ampoule prior to insertion in the injector so as toprovide a positive sealing action to prevent air ingress into thecartridge mixer upon passage of the predetermined quantity of monomerthereto.

What is claimed is:
 1. A two-component bone cement mixing systemcomprising:(A) a cartridge mixer means, having an interior volumecontaining a first predetermined quantity of a solid bone cementcomponent under vacuum pressure, for mixing said first predeterminedquantity of a solid bone cement component with a second predeterminedquantity of a liquid bone cement component in the substantial absence ofair to form a third predetermined quantity of a fluid two-component bonecement; (B) container means for holding said second predeterminedquantity of a liquid bone cement component, said container meanscomprising a hollow container body member having a longitudinal axis anda first end and a second end, said second end including a spout coaxialwith said hollow body longitudinal axis and a removable closure memberfor said spout; (C) fluid transfer means, operably connectable to saidcartridge mixer means and said container means, for fluidicallyconnecting said container means and said cartridge mixer means totransfer said second predetermined quantity of liquid bone cementcomponent from said container means to said cartridge mixer means, saidfluid transfer means comprisinga hollow injector body member having alongitudinal axis and a first open end and a second open end spacedapart on said longitudinal axis, said hollow injector body memberslidingly receivable of said hollow container body member; a cap member,disposed on said second open end of said hollow injector body member forclosure thereof, said cap member including a fluid conduit for passageof a fluid through said cap member; an elongate hollow tube, operablyconnectable to said cartridge mixer means and hermetically connectableto said fluid conduit; support means, hermetically sealingly connectingsaid second end of said hollow injector body member and said cap member,for engagingly contacting said second end of said hollow container bodymember, said support means including a fluid passage fluidicallyconnected to said fluid conduit and receivable of said spout of saidhollow container body member; (D) plug means, receivable within saidcontainer means, for automatically hermetically sealing said fluidtransfer means against passage of a material therethrough uponcompletion of the transfer of said second predetermined quantity of aliquid bone cement component from said container means to said cartridgemixer means therethrough, said plug means comprising a float memberhaving a specific gravity less than said liquid bone cement component,said float member sealingly receivable in said fluid passage in saidsupport means.
 2. The mixing system according to claim 1, wherein saidcartridge mixer means containing said first predetermined quantity of asolid bone cement component under vacuum pressure is itself containedwithin a substantially air-impermeable container under vacuum pressure.3. The mixing system according to claim 2, wherein said air-impermeablecontainer is a plastic bag.
 4. The mixing system according to claim 1,wherein said vacuum pressure in said cartridge mixer means is less thanabout 30 mm Hg.
 5. The mixing system according to claim 1, wherein saidcartridge mixer means comprisescartridge means, receivable within a bonecement gun, for containing said third predetermined quantity of a fluidtwo-component bone cement, said cartridge means including piston means,operatively engageable by said bone cement gun and moveable within saidcartridge means, for dispensing of said fluid two-component bone cementfrom said cartridge means; mixer means, detachably connected to saidcartridge means, for agitating the contents of said cartridge means,said mixer means including inlet port means, operably connectable tosaid fluid transfer means, for passage of said second predeterminedquantity of a liquid bone cement component into said cartridge mixermeans; hermetic sealing means for sealing said connected cartridge meansand mixer means against the ingress of air.
 6. The mixing systemaccording to claim 5, wherein said cartridge means comprisesa hollowcartridge body member having a longitudinal axis, and a first open endand a second open end spaced apart on said longitudinal axis; a pistonmember, axially slidable within said hollow cartridge body member,disposed within said hollow cartridge body member proximate said firstend of said cartridge body, to close said first end of said cartridgebody.
 7. The mixing system according to claim 6, wherein said mixermeans comprisesa hollow mixer body member having a longitudinal axis,and a first open end and a second open end spaced apart on saidlongitudinal axis; a cap member, disposed proximate said first end ofsaid hollow mixer body, to close said first end of said hollow mixerbody; a self-sealing aperture, formed in said cap member, operablyengageable by said fluid transfer means, for fluidic communication withsaid interior volume of said cartridge mixer means when engaged by saidfluid transfer means and sealed closure of said interior volume when notengaged by said fluid transfer means; a first aperture, formed in saidcap member, receivable of a mixing element therethrough; a movablemixing element, received in said first aperture and extending from saidinterior volume of said cartridge through said first aperture, movementof said mixing element causing agitation of the contents of saidcartridge mixer means.
 8. The mixing system according to claim 7,wherein said cartridge mixer means further comprises detachableconnection means for detachably coaxially connecting said second end ofsaid hollow cartridge body member to said second end of said hollowmixer body member.
 9. The mixing system according to claim 8, whereinsaid detachable connection means comprises a first screw thread formedon an outer surface of said second end of said hollow cartridge bodymember and a second screw thread formed on an inner surface of saidsecond end of said hollow mixer body member, said fist screw thread andsaid second screw thread being threadingly engageable of one another.10. The mixing system according to claim 7, wherein said first aperturehas an axis substantially parallel to said longitudinal axis of saidhollow mixer body member and said movable mixing element has an axiscoaxial with said axis of said first aperture.
 11. The mixing systemaccording to claim 10, wherein said mixer element is rotatably movableabout said axis of said first aperture.
 12. The mixing system accordingto claim 11, wherein said movable mixing element is axially slidable insaid first aperture.
 13. The mixing system of claim 1, wherein saidhollow container body member, said spout and said removable closuremember are made of glass.
 14. The mixing system according to claim 1,wherein said float member is a polyethylene ball.
 15. A cartridge mixer,having an interior volume, useful for the mixing of a firstpredetermined quantity of a solid bone cement component with a secondpredetermined quantity of a liquid bone cement component to form a thirdpredetermined quantity of a fluid two-component bone cement, saidcartridge mixer comprising(A) cartridge means, receivable within a bonecement gun, for containing said third predetermined quantity of a fluidtwo-component bone cement, said cartridge means including piston means,operatively engageable by said bone cement gun and movable within saidcartridge means, for dispensing of said fluid two-component bone cementfrom said cartridge means;said cartridge means comprising a hollowcartridge body member having a longitudinal axis, and a first open endand a second open end spaced apart on said longitudinal axis; saidpiston means comprising a piston member, axially slidable within saidhollow cartridge body member, disposed within said hollow cartridge bodymember proximate said first end of said cartridge body, to close saidfirst end of said cartridge body; (B) mixer means, detachably connectedto said cartridge means, for agitating the contents of said cartridgemeans, said mixer means including inlet port means for passage of asecond predetermined quantity of a liquid bone cement component intosaid cartridge mixer;said mixer means comprising a hollow mixer bodymember having a longitudinal axis, and a first open end and a secondopen end spaced apart on said longitudinal axis; a cap member, disposedproximate said first end of said hollow mixer body, to close said firstend of said hollow mixer body; a self-sealing aperture, formed in saidcap member, for fluidic communication with said interior volume of saidcartridge mixer means; a first aperture, formed in said cap meter,receivable of a mixing element therethrough; a movable mixing element,received in said first aperture and extending from said interior volumeof said cartridge through said first aperture, movement of said mixingelement causing agitation of the contents of said mixer means; (C)detachable connection means for detachably coaxially connecting saidsecond end of said hollow cartridge body member to said second end ofsaid hollow mixer body member; and (D) hermetic sealing means forsealing said connected cartridge means and mixer means against theingress of air.
 16. The cartridge mixer according to claim 15, whereinsaid cartridge mixer contains a first predetermined quantity of a solidbone cement component under vacuum pressure.
 17. The cartridge mixeraccording to claim 16, wherein said vacuum pressure is less than about30 mm Hg.
 18. The cartridge mixer according to claim 16, wherein saidcartridge mixer is contained within a substantially air-impermeablecontainer under vacuum pressure.
 19. The cartridge mixer according toclaim 18, wherein said air-impermeable container is a plastic bag. 20.The cartridge mixer according to claim 15, wherein said first aperturehas an axis substantially parallel to said longitudinal axis of saidhollow mixer body member and said movable mixing element has an axiscoaxial with said axis of said first aperture.
 21. The cartridge mixeraccording to claim 20, wherein said mixer element is rotatably movableabout said axis of said first aperture.
 22. The cartridge mixeraccording to claim 21, wherein said movable mixing element is axiallyslidable in said first aperture.
 23. The cartridge mixer according toclaim 22, wherein said mixer element comprises a plate member disposedsubstantially perpendicular to said axis of said first aperture, saidplate element being axially movable within said hollow mixer bodymember, said plate element having a plurality of holes therethrough. 24.The cartridge mixer according to claim 23, wherein said hollow mixerbody member is circular in cross-section, said plate member is circularin plan, said plurality of holes comprises a first plurality of pairs ofholes, each of said pairs of holes comprising a hole with a first radiusand a hole with a second radius, said first radius being larger thansaid second radius, each of said holes in a pair of holes being centeredon a common diameter of said plate member and disposed on opposite sidesof said plate center from one another.
 25. The cartridge mixer accordingto claim 24, wherein each hole having said first radius is immediatelyadjacent and disposed between two holes having said second radius, in acircumferential direction.
 26. The cartridge mixer according to claim25, wherein said first plurality of pairs of holes comprises three pairsof holes and the common diameter of each pair of holes is offset 60° ofarc from adjacent common diameters of holes.
 27. A two-component bonecement kit comprising:(A) a vacuum-packed cartridge mixer, defining aninterior volume, containing a first predetermined quantity of a powderybone cement component, said cartridge mixer comprising:a cartridgemember, receivable within a bone cement gun, comprising a hollow,air-impermeable cartridge body member having a longitudinal axis, and afirst open end and a second open end spaced apart on said longitudinalaxis. an air-impermeable piston member, axially slidable within saidhollow cartridge body, disposed within said cartridge body, proximatesaid first end of said cartridge body, to close said first end of saidcartridge body, releasable hermetic sealing means for releasablyhermetically sealing said piston member to said cartridge body proximatesaid first end of said cartridge body, a mixer member comprising ahollow, air-impermeable mixer body having a longitudinal axis, and afirst open end and a second open end spaced apart on said longitudinalaxis, releasable connection means for releasably coaxially hermeticallysealing connecting said second end of said cartridge body member to saidsecond end of said mixer body for fluidic communication between saidcartridge body member and said mixer body, and cap means forhermetically sealing said first end of said mixer body, said cap meansincludingself-sealing aperture means, pierceable by a hollow needle, forfluidic communication with said interior volume of said cartridge mixerthrough said hollow needle when pierced by said hollow needle andhermetically sealed closure of said interior volume when said hollowneedle is withdrawn, and mixing means for agitating a material containedwithin said interior volume of said cartridge mixer; (B) an ampoule,defining an interior volume, containing a second predetermined quantityof a liquid bone cement component, said ampoule comprising a liquid bonecement component impermeable body member having a longitudinal axis,spout means, having a predetermined diameter, for fluid communicationwith said interior volume of said ampoule and removable closure meansfor hermetically sealing said spout means; (C) an injector comprisingahollow injector body member having a longitudinal axis and a first openend and a second open end spaced apart on said longitudinal axis, saidhollow injector body member slidingly, coaxially receivable of saidampoule, a cap member, disposed on said second open end of said hollowinjector body for closure thereof, said cap member including a fluidconduit, coaxial with said hollow body, for passage of a fluid throughsaid cap member, hollow needle means, pierceable of said self-sealingaperture means, hermetically connectable to said fluid conduit, forpassage of fluid into said interior volume of said cartridge mixer,resilient support means, hermetically sealingly connecting said secondend of said hollow injector body and said cap member, for engaginglycontacting said ampoule, said resilient support means including a fluidpassage tapering toward and fluidically connected to said fluid conduit,said fluid passage coaxial with said hollow injector body and receivableof said ampoule spout means; and (D) float means, having a specificgravity less than said liquid bone cement component, for hermeticallysealingly closing said fluid passage in said resilient support means.28. The bone cement kit according to claim 27, wherein said float meanscomprises a polyethylene ball.
 29. A method of preparing a bone cementcomprising:providing a cartridge mixer means, having an interior volumecontaining a first predetermined quantity of a solid bone cementcomponent under vacuum pressure, for mixing said first predeterminedquantity of a solid bone cement component with a second predeterminedquantity of a liquid bone cement component in the substantial absence ofair to form a third predetermined quantity of a fluid two-component bonecement; providing container means, containing said second predeterminedquantity of a liquid bone cement component, for holding a liquid bonecement component; cooling said cartridge mixer means containing saidsolid bone cement component and said container means containing saidliquid bone cement component to a temperature less than 20° C.; thenadmixing said liquid bone cement component and said solid bone cementcomponent in said cartridge mixer means while maintaining said vacuumpressure in said cartridge mixer means.
 30. The method according toclaim 29, wherein said cooling is to a temperature of less than 15° C.31. The method according to claim 29, wherein said cooling is to atemperature of about 12° C.
 32. The method according to claim 29,wherein said vacuum pressure is less than about 30 mm Hg.
 33. Atwo-component bone cement mixing system comprising:(A) a cartridge mixermeans, having an interior volume containing a first predeterminedquantity of a solid bone cement component under vacuum pressure, formixing said first predetermined quantity of a solid bone cementcomponent with a second predetermined quantity of a liquid bone cementcomponent in the substantially absence of air to form a thirdpredetermined quantity of a fluid two-component bone cement;saidcartridge mixer means comprising(a) cartridge means, receivable within abone cement gun, for containing said third predetermined quantity of afluid two-component bone cement, said cartridge means including pistonmeans, operatively engageable by said bone cement gun and moveablewithin said cartridge means, for dispensing of said fluid two-componentbone cement from said cartridge means;said cartridge means comprisingahollow cartridge body member having a longitudinal axis, and a firstopen end and a second open end spaced apart on said longitudinal axis;said piston means comprising a piston member, axially slidable withinsaid hollow cartridge body member, disposed within said hollow cartridgebody member proximate said first end of said cartridge body, to closesaid first end of said cartridge body; (b) mixer means, detachablyconnected to said cartridge means, for agitating the contents of saidcartridge means, said mixer means including inlet port means, operablyconnectable to said fluid transfer means, for passage of said secondpredetermined quantity of a liquid bone cement component into saidcartridge mixer means;said mixer means comprisinga hollow mixer bodymember having a longitudinal axis, and a first open end and a secondopen end spaced apart on said longitudinal axis; a cap member, disposedproximate said first end of said hollow mixer body, to close said firstend of said hollow mixer body; a self-sealing aperture, formed in saidcap member, operably engageable by said fluid transfer means, forfluidic communication with said interior volume of said cartridge mixermeans when engaged by said fluid transfer means and sealed closure ofsaid interior volume when not engaged by said fluid transfer means; afirst aperture, formed in said cap member, receivable of a mixingelement therethrough; a movable mixing element, received in said firstaperture and extending from said interior volume of said cartridgethrough said first aperture, movement of said mixing element causingagitation of the contents of said cartridge mixer means; (c) detachableconnection means for detachably coaxially connecting said second end ofsaid hollow cartridge body member to said second end of said hollowmixer body member; (d) hermetic sealing means for sealing said connectedcartridge means and mixer means against the ingress of air; (B)container means for holding said second predetermined quantity of aliquid bone cement component; (C) fluid transfer means, operablyconnectable to said cartridge mixer means and said container means, forfluidically connecting said container means and said cartridge mixermeans to transfer said second predetermined quantity of a liquid bonecement component from said container means to said cartridge mixermeans; (D) plug means, receivable within said container means, forautomatically hermetically sealing said fluid transfer means againstpassage of a material therethrough upon completion of the transfer ofsaid second predetermined quantity of a liquid bone cement componentfrom said container means to said cartridge mixer means therethrough.34. A cartridge mixer, having an interior volume, useful for the mixingof a first predetermined quantity of a solid bone cement component witha second predetermined quantity of a liquid bone cement component toform a third predetermined quantity of a fluid two-component bonecement, said cartridge mixer comprising(A) cartridge means, receivablewithin a bone cement gun, for containing said third predeterminedquantity of a fluid two-component bone cement, said cartridge meansincluding piston means, operatively engageable by said bone cement gunand movable within said cartridge means, for dispensing of said fluidtwo-component bone cement from said cartridge means;said cartridge meanscomprisinga hollow cartridge body member having a longitudinal axis, anda first open end and a second open end spaced apart on said longitudinalaxis;said piston means comprisinga piston member, axially slidablewithin said hollow cartridge body member, disposed within said hollowcartridge body member proximate said first end of said cartridge body,to close said first end of said cartridge body; (B) mixer means,detachably connected to said cartridge mans, for agitating the contentsof said cartridge means, said mixer means including inlet port means forpassage of a second predetermined quantity of a liquid bone cementcomponent into said cartridge mixer;said mixer means comprisinga hollowmixer body member having a longitudinal axis, and a first open end and asecond open end spaced apart on said longitudinal axis; a cap member,disposed proximate said first end of said hollow mixer body, to closesaid first end of said hollow mixer body; a self-sealing aperture,formed in said cap member, for fluidic communication with said interiorvolume of said cartridge mixer means; a first aperture, formed in saidcap member, receivable of a mixing element therethrough; a movablemixing element, received in said first aperture and extending from saidinterior volume of said cartridge through said first aperture, movementof said mixing element causing agitation of the contents of saidcartridge mixer means; wherein said first aperture has an axissubstantially parallel to said longitudinal axis of said hollow mixerbody member and said movable mixing element has an axis coaxial withsaid axis of said first aperture, said mixer element is rotatablymovable about said axis of said first aperture, said movable mixingelement is axially slidable in said first aperture, and said mixerelement comprises a plate member disposed substantially perpendicular tosaid axis of said first aperture, said plate element being axiallymovable within said hollow mixer body member, said plate element havinga plurality of holes therethrough; (C) hermetic sealing means forsealing said connected cartridge means and mixer means against theingress of air.
 35. The cartridge mixer according to claim 34, whereinsaid hollow mixer body member is circular in cross-section, said platemember is circular in plan, said plurality of holes comprises a firstplurality of pairs of holes, each of said pairs of holes comprising ahole with a first radius and a hole with a second radius, said firstradius being larger than said second radius, each of said holes in apair of holes being centered on a common diameter of said plate memberand disposed on opposite sides of said plate center from one another.36. The cartridge mixer according to claim 35, wherein each hole havingsaid first radius is immediately adjacent and disposed between two holeshaving said second radius, in a circumferential direction.
 37. Thecartridge mixer according to claim 36, wherein said first plurality ofpairs of holes comprises three pairs of holes and the common diameter ofeach pair of holes is offset 60° of arc from adjacent common diametersof holes.